Field of the Invention
The invention is directed to medical devices used to assist walking by helping to support a user's weight. The invention is illustrated with respect to a crutch.
Background Information
Several medical conditions require that a patient reduce the part of his weight which is borne by one or both legs. A common tool for assisting in doing so is the crutch, which conceptually comprises a support designed and angled to fit under a user's axilla (an axillary support) or a support shaped so as to make contact with the ulnar border of the user's forearm (a short-arm support), connected by a shaft to a lower end terminating in a tip designed to contact the ground, with a handgrip intermediate between the two ends and essentially perpendicular to the shaft so as to enable the user to support a portion of his body weight with his arm and shoulder.
In some prior art embodiments, two shafts extend from the axillary support, enclose the handgrip, then taper together and are joined to a single shaft leading to the tip.
It is convenient to describe the orientation of the crutch with respect to the user—for example, forward meaning in the direction the user is facing and outward meaning to the side and away from the user. With these terms defined, the definitions of “backward” “inward” “upward” and “downward” are used in their normal senses.
In the most common embodiments in use, a patient typically positions the axillary support of the crutch below the axilla, pressing it against his ribcage and grips the handgrip, with elbow flexed.
In order to use a pair of crutches to walk while avoiding placing weight on an injured foot, the user stands on the uninjured (weight bearing) foot with a crutch in each hand as just described. The tip of each crutch is placed about six to twelve inches outward and in front of the associated foot. FIG. 3 illustrates this position. The patient then shifts his weight to the crutches, supporting the weight with his arms and swings his body forward between the crutches and transfers his weight to the uninjured foot.
Prior art crutches tend to force the user's arm to be too extended, the orientation of the handgrip forces the user's hand to be radially deviated or flexed and the top of the crutch to dig into the user's chest, all of which are uncomfortable positions and, more specifically, force the user's hand, elbow and shoulder to assume non-anatomic positions for support of weight. Crutches used improperly or for an extended period of time may cause injury to the user's axillary nerves, vessels and tendons resulting from supporting the user's weight, injury to the user's arm or elbow from the stress of maintaining balance or injury to the user's hand or wrist resulting from the stressful position of the user's hand and wrist required to grip conventional handgrips. In addition, because of the anatomy of the axilla, prior art crutches lend themselves to improper use which compresses axillary veins, resulting in swelling of the user's arm.
Prior art attempts to reduce these injuries include padding the axillary or short-arm support and handgrip.
Prior art crutches also encourage an inherently unstable stance. In order to hold a pair of crutches in a strong supporting position, a user tends to hold the upper end of each crutch close against the user's side, providing as a consequence a short distance between the tips of the two crutches, since the crutches extend essentially parallel to the user's side. The distance between the tips may be thought of as the base for supporting the user's weight. If the user holds the upper end of the crutches as described but angles them out so as to increase the distance between the tips in an effort to provide a more stable base, the tips will contact the ground at an angle and be more prone to slipping. This will also lead to the top of the crutch putting pressure on the axilla.